If I can make a suggestion, you might want to look into the structure of the blockchain networks that use a network of known super-nodes to watch and verify each other.
If you have hundreds of known, diverse nodes distributed globally (run by very different institutions like Harvard, Bank of America, the Vatican, the Red Cross, the Gates Foundation, the House of Saud, etc. etc.) they can all watch each other, and the odds of them all going offline at the same time or cooperating to deny a specific user's transactions are very low.
This is called delegated byzantine fault tolerance, and what blockchains like NEO and ARK use this, or a variation of it to provide consensus. Token holders basically "elect" the super nodes, and if any begin to act untrustworthy they are "voted out." I'm a fan of this consensus styles because blockchains become semi centralized over time. Maybe not in the technical full validating node way, but certainly politically centralized.
If you have hundreds of known, diverse nodes distributed globally (run by very different institutions like Harvard, Bank of America, the Vatican, the Red Cross, the Gates Foundation, the House of Saud, etc. etc.) they can all watch each other, and the odds of them all going offline at the same time or cooperating to deny a specific user's transactions are very low.